1. Field of the Invention
The present invention relates to a motion control system for a vehicle having at least two driving wheels driven by a driving power source such as, e.g., a combustion engine or an electric motor.
2. Discussion of the Related Art
Heretofore, as a motion control system for a two-wheeled vehicle or a four-wheeled vehicle, there has been known a “Behavior Control Device for Vehicle” described in Japanese Patent No. 3463622 (equivalent of U.S. Pat. No. 6,324,458 B1). In the behavior control device, it is judged whether the rolling liability detected by rolling liability detecting means for detecting the rolling liability of a vehicle is equal to or greater than a predetermined rolling liability or not, and when the rolling liability detected by the rolling liability detecting means is equal to or greater than the predetermined rolling liability, control is performed to suppress the rolling liability of the vehicle.
More specifically, the output torque of an engine 10 is controlled to become a target output torque which is adjustably decreased by an output torque regulation amount ΔTe, whereby the vehicle is decelerated (step 250) to suppress the rolling liability of the vehicle.
Further, a hydraulic circuit 44 is controlled on the basis of brake control amounts Fbi, and the brake forces to respective wheels are controlled in dependence on the respective brake control amounts Fbi for the respective wheels under the control of wheel speed feedback or brake pressure feedback, whereby the rolling liability of the vehicle is suppressed. That is, the brake control amounts Fbfdi for the respective wheels are calculated so that the vehicle is decelerated and is given a yaw moment in the direction toward decreasing the turn yaw moment without suffering the spinning of the vehicle body, for example, so that predetermined brake forces are applied to the wheels except for an inside front wheel during a turn.
By the way, in the aforementioned behavior control device, a large effect in suppressing an over-rolling has been obtained by lowing the engine output or by applying brake forces to predetermined wheels when the over-rolling occurs on the vehicle. Thus, since the feeling about the deceleration of the vehicle (the feeling about the operation under a rolling suppression control) is also strong, there arise a problem that the drive feeling is deteriorated to make the driver have an unpleasant feeling against his manipulation. Further, since the rolling suppression control is made to begin with a substantial delay in order that the timing at which such a bad drive feeling is given is to be delayed as long as possible, there arises an additional problem that the rolling suppression control is started for the first time after the rolling becomes excessive.